1. Field of the Invention (Technical Field)
The invention relates to apparatuses for dissipating vibrational energy in static and non-static structures, for example, civil structures and space platforms, respectively, and methods for their use.
2. Background Art
The past two decades have witnessed substantial activity in the area of vibration control of structures. Traditionally, detection by sensors and application of out-of-phase forces have been employed. U.S. Pat. No. 4,841,685, to Masri, et al., entitled Controllable Damper; U.S. Pat. No. 4,429,496, to Masri, entitled Method and Apparatus for Active Control of Flexible Structures; and U.S. Pat. No. 4,929,874, to Mizuno, et al., entitled Vibration Control System, are all representative of this approach. Such systems require tremendous energy, are subject to overcorrection and modal spillover, and are basically limited to correction of the swaying mode of vibration.
U.S. Pat. No. 4,742,998, to Schubert, entitled Active Vibration Isolation System Employing an Electro-Rheological Fluid; U.S. Pat. No. 3,807,678, to Karnopp, et al., entitled System for Controlling the Transmission of Energy Between Spaced Members; and U.S. Pat. No. 4,921,272, to Ivers, entitled Semi-Active Damper Valve Mean with Electromagnetically Movable Discs in the Piston, all relate to variable damping means for limiting transmission of vibration.
U.S. Pat. No. 4,910,929, to Scholl, entitled Added Damping and Stiffness Elements, discloses the combination of damping and stiffness elements to optimize earthquake response in static buildings.
U.S. Pat. No. 4,799,339, to Kobori, et al., entitled Method of Controlling Building Against Earthquake, discloses a method of remotely sensing earthquake tremors and changing the resonant frequency of a static building based upon such remotely sensed tremors.
U.S. Pat. No. 4,635,892, to Baker, entitled Active Vibration Suppressor discloses a seismic mass movable in a direction opposing structural displacement.
Japanese Patent No. 59-205036, to Furukawa, entitled Earthquake-Proofing Device, discloses electromagnets for correcting positional deviation of the Structure.
The publication entitled Active Seismic Response Control Systems for Nuclear Power Plant Equipment Facilities, by Kobori, et al., discloses an active seismic response system which adjusts the structural resonant frequency to avoid resonant vibration.
None of the above references disclose an apparatus and method of sensing and measuring total energy, potential and kinetic, solely within a structure, static or non-static. Further, none of the references disclose an apparatus and method for dissipating such total energy by altering structural stiffness, thereby altering the modal energies of vibration of the structure.